Synergistic band structure tailoring and texturing enhance cooling-power generation Bifunctionality in Bi_0.4Sb_1.6Te₃

High-performance thermoelectric devices capable of both cooling and power generation hold significant application prospects. However, this imposes high requirements on the room-temperature and wide-temperature-range performance of thermoelectric materials. In this work, we find an unusual narrowing of band gap in Bi_0.4Sb_1.6Te₃, along with non-parabolic band feature that is beneficial to a larger effective mass. Based on this finding, we propose a synergistic strategy to enhance BiSbTe-based material performance across wide temperature ranges. By precisely tuning the Bi/Sb stoichiometric ratio, carrier concentration, via hot deformation (HD) treatment, Bi_0.398Pb_0.002Sb_1.6Te₃-HD simultaneously achieves an enhanced room-temperature ZT value of 1.1 and a high average ZT of 1.16. Benefiting from this good performance, a 127-pair thermoelectric module demonstrates a competitive high conversion efficiency of 5.8 % under ΔT = 170 K and a maximum cooling temperature difference (ΔT_max) of 68.3 K at 300 K, outperforming commercial Bi_0.5Sb_1.5Te₃ module. This dual-functionality potentially makes the BiSbTe-based materials ideal for waste heat recovery in industrial systems, portable cooling systems, and hybrid energy management scenarios.